The role of the medium on the acid dissociation constants of some azo dyes in view of experimental and theoretical data

✍ Scribed by Y.H. Ebead

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 841 KB
• Volume: 982
• Category: Article
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2010.08.013

✦ Synopsis

In this study, the pK a values of some azo dyes derived from cyclohexane-1,3-dione in different organic solvent + water mixtures have been determined spectrophotometrically. The organic solvents used are ethanol, acetone and N,N-dimethylformamide (DMF). Thus, the nature and the proportion of the organic cosolvent effects as well as the molecular structure on acidity constants were evaluated. Furthermore, the proton-donating ability of N 10 H reflected by thermodynamic parameters -D f,298 H o , D 298 S o and D f,298 G ofor compounds 1-4 has been estimated using AM1and PM6 methods in the gas and aqueous phases. The data obtained provides a complete and accurate picture of the acid-base properties of the compounds under study. The pK a values predicted in aqueous phase by the previous methods were compared with the experimental values and the best agreement with the experimental data was obtained by AM1.